(a) Field of the Invention
The present invention relates to a metal-separator for a fuel cell stack, and more particularly to a structure for improving laminating efficiency of a metal-separator for a fuel cell stack in which an edge of the separator comprises an embossed structure so that a plurality of the separators can be stably laminated in a honeycomb structure.
(b) Background
FIG. 1 is an exploded perspective view of a conventional polymer electrolyte fuel cell, and FIG. 2A and FIG. 2B are top plan views thereof.
As shown in FIG. 1, a polymer electrolyte fuel cell stack 1 includes a membrane electrode assembly (MEA) 3 which is comprised of a polymer electrolyte membrane and electrodes formed on both sides of the polymer electrolyte membrane. It also includes a pair of gas diffusion layers 4 which are coupled to the membrane electrode assembly 3 and deliver reaction gases to the electrodes. It also includes a pair of conductive separators 6 which adhere to outer surfaces of the respective gas diffusion layers 4 so as to supply reaction gases. It also includes a gasket 5 which is interposed between the membrane electrode assembly 3 and the separator 6 so as to prevent the reaction gases from being leaked and to seal a gap. In addition, current collectors 7 and connecting plates (end plates) 8 are coupled to the outside of the separator 6, thereby forming the fuel cell stack 1.
The separator 6 separates hydrogen and oxygen, electrically connects the membrane electrode assembly 3, and supports the membrane electrode assembly 3 to maintain the shape of the fuel cell stack 1.
Accordingly, the separator should have a rigid structure for preventing the two gases from being mixed, an excellent electrical conductivity for serving an electrical conductor, and a high strength for serving a support member.
However, since voltage generated by one unit cell (basic unit of a fuel cell which is formed by coupling the membrane electrode assembly, the gasket, and the separator) is small, tens or hundreds of unit cells should be laminated in order to produce a desired electric power.
In the case that a lot of unit cells are laminated, if the separator cannot maintain a constant surface pressure, the separator may be locally deformed so that the sealing cannot be maintained. There have been many structures suggested to overcome this problem. Such structures, however, have a complicated sealing structure, causing the forming process to be complicated and limiting the degree of freedom in the development of design.
There is thus a need for an improved structure that can overcome the problems.